Brake



7 Oct. 11, 1938.

P. KARLAK El AL BRAKE Filed April 3, 1937 3 INVENTOR PE TEE. 6IR. L82 IQAQTHU fie W H mm Q w w H N mfi Mm R O. STONE 3 ATTORNEY Patented Oct. 11, 1938 This invention PATENT OFFICE BRAKE Peter Karlak and Arthur 0; Stone, Rutherford,

App1icationhpril 3,1937, SeriaLNo. 134,700

4 Claims.

relates to brake mechanisms,

and more particularly to brakes of the internal expansion type generally used for automotive vehicles. In brakes f the abovetype, it is customary practiceto establish frictional contact between a plurality of brake shoes having a fabric lining on the acting surface of each shoe, with the inner surface of is carried by the establish contact expand radially until againstthe drum.

a great deal on perfect circumfer shoe with respect to the drum surface. brake shoes heretofore use a revolving steel drum. The latter revolving wheel. Inorder to the brake shoes arecaused to the lining-is :firmly pressed The retarding force depends the area of contact and the ential alignment of each brake The d were usually pivoted around an eccentric pin at one end, the expand- 'ing force acting, on the the above manne was necessary to e and its acting surface other end thereof. In r, angular motionof the .shoe stablish contact with the drum; diminished towardthe A structure :of this type ex: perfect circumferential, align- .A feature of th s invention is the eliminationv of angular motion of the brake shoes and the provision of means for perfect circumferential alignment between and the drum.

A marked disa the acting surface of the shoe dvantage of all brakes the type above mentioned, employing a pluralityof shoes to contact the drum simultaneously, resides in the fact that drum by each shoe This is due. uneven wear of the lining, sion of the metallic parts equal.

of production an the pressure exerted on the -may not be at all times to several factors, such as differences of .ex'pan by heat, tolerances d assembly which often vary within wide limits. I

"Another, and important feature of this invention is the provision of inexpensive and simple means whereby equalization ofpressurebetween the shoes is automatically established atall times, irrespective of differences caused by wear, heat or assembly tolerances. I

These and other features of the invention will from the following specification, taken in connectionwith the accompanying drawing in which:

Fig. l is a transverse section view of the brake mechanism in accordance with this invention, taken on the plane of. the line l-l of Fig. 2.

Fig. 2 is a plan invention.

view of a brake embodying this outwardly.

mechanism. r 4 is a mo ing means shown in Fig. 2. a i .Fig. .5 illustrates the application of fluid pressure operation of the brake. I

Referring to the accompanyingdrawing wherein identical reference characters designate identical parts, the description will follow Fig.2, as the-one which illustrates the invention in the greatest detail. y i

The various figures of the drawing show the invention as applied to the wheel ofa motor vehicle 'It is to be understood that no restriction of its, application is intended thereby, and the illustration is merely invention can be adapted in general to all types of rotating bodies which require frictional brake devices.

It is seenthat the brake mechanism consists of the housing or drum l which may be mounted upon the wheel 2 of the vehicle by any suitable manner, such as shown by the bolts 3, in Fig. 1. The drum I revolves around the axis of the wheel and the inner surface thereof is used for the frictional retardation of motion. Fitting within the brake drum I, with sufiicient clearance to allow motion thereof is a shield plate 4.

dification of the pressure equaliz The latby way of example. The

and carries vertically running slots 5, for receiving the. anchoring studs 6. the slots Swill be described in'more detail later.

A pair of brake shoes In are disposed concentrically within the with 'a lining I2, of the conventional fabric used generally for automotive brakes. It is to be noted that'the shoes ID are in the shapeof an arc,:that is semi-circles which follow the curva ture of the drum I. both ends into a fiattenedportion l3 which is provided with a cut-out to receive the, roller 9 which turns around a pin l4 driven into the end portion l3 of the shoe ID. Two supporting brack ets I, each having a grooved surface 8 into which the rollers 9 fit snugly, act as a platform upon which the shoes 10 may slide inwardly or shoes 3|, towards the drum l' or receding from it, is uniformly radial at any peripheral point thereonandwith equal freedom of movement at both ends thereo-f. The recessed groove .8 of the bracket 1 holds the shoes firmly by the rollers 9 preventing any co-axial motion which would otherwise cause chattering. The slots 5 in the shield plate 4, previously mentioned, permit exdrum. Each shoe is fitted Each shoe IE! is bent at In other words, the motion of the I p '30 The function of act vertical fitting of the bracket 1, and the support of the shoes it! in this manner permits a quick and easy assembly. By simply loosening the bolts 6, the brackets 7 may be lowered sufliciently to disengage the rollers 9 from the groove 8 and the removal of a shoe It], for example for the purpose of replacement, becomes a simple matter.

Each of the brake shoes i is provided on its inner surface with a pair of wedge-shapedcams l5 so coordinated as to form a progressively inclined riding surface for the rollers E6 of the star wheel [1. A pair of springs 18, each located in a housing 31 which mounts on the outer surface of the shield plate 4, are so arranged as topress the shoes I!) by the abutment 36 provided; on the bottom surface of each cam l5 inwardly and maintain the cams 15 in close contact with the rollers !6. The function of springs l8 will become more apparent in the description of the operation of the brake mechanismh A star wheel ll having a plurality of radially extending arms I 9, evenly spaced, is rotatably arranged around the axis of the wheel; each of the arms I9 terminates in'a roller l6, previously mentioned, which rides over the progressively inclined surface of one of the cams IS. The number of the arms is shown here is four inasmuch as there are two cams l5 for each shoe 10. How-- ever, this number may varywith different types of brakes depending upon the construction and number of brake shoes employed. Another arm of the star wheel I1, designated as the arm 31,

is arranged to engage the two-lobe cam 22, each lobe of the latter functioning as a crank imparting motion to the star wheel I! by means of the arm 3!. The cam 22 is actuated by a cam rock shaft 23, journaled in a bearing 24 suitably secured to the shield plate 4. The shaft 23 extending through the plate 4 serves as the actuating means of thebrake and may be coupled to the brake pedal, or lever, not shown here.

The. rotatable mounting 'of the star "wheel 'I'I comprises the inner flange 20 of the axle housing H and the spacer ring assembly 2|, fitting over said flange and thestar wheel I! in turn fitting over the ring 2!. The function of the ring 2| is of utmost importance, it being the means permitting radial pressure equalization between the brake shoes '5. A detailed description of its construction shall be given here.

In the preferred embodiment of this invention,

shown in Figs. 1 and 2,the spacerring. assembly 21,

comprisesa ring 25 in the form of a ring of solid but resilient medium such as rubber, imbedded between telescoping housings 26 and 27 'of sheet metal or similar material. The outer housing is suiiiciently large in size to fit over and permit the telescoping therein of the inner housing 21. The resiliency of the rubber ring 25 tendsto keep the housing 26 and 27 uniformly spaced. A force acting radially on'the housing 26 will compress the two housings in such manner, that at the point of pressure, the housing 21 telescopes into the housing 26 and at the point diametrically opposite tothe point of pressure, slides out of the housing 26, to portionate with the telescoping at the point of pressure. Pins 28 driven through the telescoping housing 26 and the rubber ring 25, fasten securely to the housing 27, whereas the heads of the pins 28 locate in suitable recesses 29 provided in the hub portion of the star wheel IT. The holes in the ring 25 and the outer housing 26 through which the pins 28 pass are sumthe housing 21 an extent proof the housings 1 is bent over a pin 32 located in the plate 4.

ciently large to permit free movement of the housing 26 over the housing 21 in a radial sense. The function of the pins 28 is to locate the ring assembly 2| within the hub portion of the star wheel I? in such a Way that both may rotate together without friction between them. In this manner, the ring assembly 2! becomes a semiintegral part of the hub of the wheel H riding over the inner flange 29 of the axle housing II. A tension spring 30 hooks into the arm 3! of the star wheel I! at one end, while its other end actuating arm 3! of the star wheel, 11 held against the cam 22.

Let us consider now the operation of the brake is thereby mechanism constructed in accordance with this invention;

1 I In Figs. 1 and 2, the brake is illustrated in the open or de-energized position. The mechanical structure of the assembly and the coordination .of its elements being of .a'simplenature, a view showing the energized position has been omitted, inasmuch as anybody skilled in the art can readily visualize the second alternative position.

Rotation of the star wheel I? in a clock-wise direction is effected bythe turning of the two lobe cam 22in any direction. The latter as previously stated, is actuated by the shaft 23 connecting .with the brake lever, not shown here. Assuming clock-wise rotation of the star wheel IL'the rollers E6 of the arms [9 riding over the in actual practice,theoretical uniformity is impossible even when'close tolerances are maintained at increased production costs. Furthermore, in actual use, conceding the attainment of perfect symmetry, un'even wear would shortly disbalance the assembly. 7 7

However, in accordance with this invention, means are providedior maintaining efiective uniformity and equalization of radial pressurewhich comprises the novel "support of the star wheel H, permitting its eccentric allocation automatically in proportion with conditions of asymmetry.

Let us consider, for example, that due to unevenness, irrespective of its "cause, one of the shoes Ill, be itthe one on the left-hand side, contacts the drum I before the othershoe; The turning of the cam 22 forces the star wheel ii and the rollers i6 to ride over. the cams 15 of the shoe inquestion and the latter being already in contact with the drum i is prevented from further; motion andibecoines a transmitter of force, causing the star wheel ll to move out of its concentric allocation. In this example to the right, the action of the spacer ring 2| now becomes evident. Being compressible, it permits eccentric motion of the star Wheel. The housings 26 and 2? telescope and compress the rubber ring 25 at the point of pressure. The shifting of the star wheel H to the right-following the example-will immediately press the shoe H! on the right-hand side, againstthe-drum, until both the shoes press equally against it. whereupon, the

The

star wheel becomes fixed as far as eccentric motion is concerned.

Upon reverse motion of the cam 22, the star wheel I! is returned to its original position by the spring 30. Similarly, the brake shoes are repositioned by the springs l8.

Referring to the modification shown in Fig. 3, the repositioning'springs l8 are dispensed with and the arm ii) of the star wheel 11, has its roller 16 arranged to slide in a slot 33 provided in the cam W of the shoe Ii). In this manner, the reverse motion of the star wheel l1 resets the shoes Ill. The spring 30, therefore, is of heavier gauge, being the resetting force for all the moving parts.

The modification shown in Fig. 4, refers to the spacer ring 2|, in which, instead of the rubber inner ring 25, a plurality of radially disposed springs 25' are arranged within the telescoping I sleeves 26 and 21, and act as the resilient medium to permit eccentric displacement of the star wheel IT.

A modification of the actuating means for the star wheel i1 is shown by way of example in Fig. 5. Instead of the two-lobe cam 22 previously described, the actuating arm 3! of the star wheel I? is positioned directly by the plunger arm 34 of a fluid compression device generally used with hydraulic brake systems.

What is claimed is:

1. In a brake, a revolving drum, a pair of concentrically arranged brake shoes slideably mounted upon supports, said shoes being independently moveable in a radial sense to contact the inner surface of said drum, means for transmitting motive force simultaneously to each shoe, comprising a star wheel having a plurality of arms each adapted to ride over a progressively inclined surface on said shoes, whereby the rotation of said wheel causes radial displacement of said shoes and means for journaling said wheel concentrically with the axis of said drum, said means including a resilient ring support permitting eccentric motion of said wheel.

2. A brake, comprising a rotary brake drum, a shield plate, a pair of brake shoes in concentric alignment with said drum each being in the shape of an arc terminating in inwardly bent portions fitted with rollers, a pair of grooved supporting brackets mounted on said plate and so adjusted as to engage said rollers in said grooves whereby said shoes may slide inwardly and outwardly, spring means urging said shoes inwardly, a pair of cams carried by each of said shoes, a star wheel having a plurality of radially extending arms terminating in rollers engaging said cams, spring means urging one arm of said Wheel against a lobed cam, resilient means for journaling said wheel upon the axle housing of said drum including a rubber ring betweentelescoping members whereby said wheel may be positioned eccentrically to its axis of rotation,

3. In a brake, a star wheel adapted to actuate a plurality of brake shoes simultaneously, means for journaling said wheel upon the axle housing of a rotating body, including a compressible housing in the form of a sleeve placed between the inner flange of said axle housing and the hub of said wheel, said sleeve enclosing a plurality of radially arranged spring members.

4. In a brake, a revolving drum, means for radially moving a plurality of brake shoes, comprising a star wheel rotatably arranged having a plurality of radially extending arms each adapted. to engage slots in said shoes, said slots being so coordinated as to form a progressively inclined path for said arms whereby rotation of said wheel in one direction causes outward motion of said shoes and rotation in the opposite direction inward motion thereof, and means for journaling said wheel concentrically with respect to said drum, said journaling means including a resilient ring support permitting eccentric motion of said wheel.

PETER KARLAK.

ARTHUR/O. STONE. 

